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Joined: Aug 2021
Posts: 9
Likes: 1
RodP Offline OP
I recently bought a well used Masport Shiremaster 720 self-propelled slasher/HD mower. The seller had the whole unit painted black, most likely to hided the surface rust and many knocks, etc. Thankfully the Honda GV400 engine was left la natural, be it the red was somewhat faded.

I was confident that I would be able to do it up and make good use of it on our bush block. However, there were three things that needed to be looked at: the main drive shaft, the in-line differential and the top cover plate.

Firstly the main through drive shaft was badly worn in the main bearing areas. The respective bronze bushing, held in both ends of the rear wheel frame assembly, had worn right down to the steel frame. To simply overcome both the worn-down shaft and the worn-out bushings, I purchased and pressed in longer bushings (twice as long) that would align up with the the un-worn areas of the shaft.

Secondly, the through-shafted in-line differential also had worn bushing, but not as bad. I was easily able to replace the external bushings, so I did, but left the blind internal bushing as is.
The diff. housing has a boss/lug acting as floating torque arm to the main frame, with the main shaft passing right through the diff. to both driving wheels. The LH wheel is fixed to the shaft and driven from the LH output of the diff. The RH wheel is sleeved and can counter-rotate (when cornering) on the outside of the main shaft, driven directly via a sleeved drive-dog out the RH output of the diff.
The high speed input shaft dirven by a friction wheel runs into the diff. through the torque arm boss/lug.
I admit I had never seen an in-line differential. before, and I was impressed with the condition inside, well engineered and very little shaft wear.

Thirdly, the top cover plate was missing and needed to be replaced. Most likely it's main purpose was to be a safety guard, as well as restricting any objects falling in and getting tangled-up in the mechanisms.
I thought about making a replacement out of folded sheet metal, as the original likely was. Without a bender or any sheet metal equipment, I decided it would be easier and neater to make it out of plywood.
To maintain some internal height clearances and to allow for some moving parts, strips of timber were nailed and glued under and around thee sides. A hole for the hold-down bolt, and a long slot for the F-R direction indicator were made in the ply top. Finally a coat of outdoor paint.

Admittedly, the condition of the Honda GV400 engine was unknown, although I did start it before I paid any dollars. It ran, but a bit rough. The seller had bought a third-party carburettor to replace the original one and had trouble fitting it, and so threw it in as a sweetener. I checked out the new carby on the web, and discovered many sites were promoting it as the "best" replacement, but with a manual choke. Certainly an el cheapo.
I really preferred to use the original Honda carby if possible. So I completely stripped, checked, cleaned and reassembled it. Other than a little corrosion on the bowl stem and thread, everything checked out as new. After completely cleaning the fuel tank and flushing the fuel lines and tap, the best part was after a cough and splutter the engine actually started on the first pull, and ran up smoothly. Only a Honda!

I was keen to give it a reasonable test run, and it ran like a beast, lots of power. The only issue is it really needs a diff-lock option when working on uneven ground.
Yes, I still have some improvements to do over time to bring it up to "near as original".
All round I am very happy with this machine. Like most machinery of it's era, it was built like a brick sh*thouse, and designed for long-term.

Attached Images
ShiremasterDiff_combo.jpg (98.57 KB, 79 downloads)
Shiremaster720.jpg (120.5 KB, 78 downloads)
Last edited by RodP; 21/10/21 10:08 AM.
1 member likes this: N1KK0
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Joined: Nov 2013
Posts: 6,938
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Forum Historian
Hello RadP

This one has not gone un-noticed.

ODK members will appreciate a fair and balanced review,
nicely written and illustrated.

Many thanks from ODK for adding to the record on the
Masport Shiremaster 720.



Joined: Sep 2021
Posts: 1
What condition is the power transfer in RodP? I bought an old one this year too - and it runs ok, but i think i've lost a bit of speed as the tyre is in pretty ordinary shape. It does a great job though - plows through anything!

Joined: Aug 2021
Posts: 9
Likes: 1
RodP Offline OP
Hi wallyscr,
Not sure what you mean by power transfer. Are you are referring to the high speed input shaft to the gearbox which has a rubber "tyre" that makes contact with and is driven by the infinitely variable spinning friction wheel? If so, yes the rubber "tyre" is somewhat hard now and has lost its grabbing ability, and as such, is very likely not transferring anywhere near its as-new capacity in speed and torque.
However, like yours, my Shiremaster is a real beast, sometimes a little hard to fully control.
And yes, I do need to procure and replace this Tyre (P/N -187) I am sure it would make a big improvement. Then hang on!

Last edited by RodP; 15/12/21 10:33 PM.

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